To coat workpieces, coating devices, for example electrostatic rotary atomizers or colour changers are usually used, to which the coating agent to be applied is fed, for example by means of a valve, for example a coating agent valve.
The valves in painting technology are usually constructed with a round pneumatic piston, it being possible for the pneumatic drive of the valve to take place via a control air space, a piston seal and a spring, which are situated in a round housing. A cylinder, in which a movable valve needle is arranged, is usually formed in the round housing. During operation, the valve needles are therefore exposed to the coating agent applied in each case and have to be cleaned, for example by brief flushing with air. Owing to the arrangement of the valve needles in coating agent cylinders, such cleaning is however difficult for design reasons. The coating agent valves are also screwed into the coating agent devices on the discharge side, so they have to be unscrewed for cleaning or maintenance purposes, with a great deal of effort. Such threaded connections furthermore do not permit a tighter arrangement of the coating agent valves in a coating agent device, which reduces system efficiency. The known coating systems with such coating agent valves and coating agent devices are therefore high-maintenance and inefficient.
Some known valves are furthermore constructed multiple materials, e.g., stainless steel and plastic. These pairs of materials are usually connected using screw-fastenings, adhesives, injection moulding transversely to the axis of symmetry of the valve needle. These pairs of materials result in abrasion during use, which entails an increased maintenance frequency.
Reference is also made to EP 1 157 747 A2 and corresponding U.S. Pat. No. 6,315,168.
Accordingly, there is a need for a more efficient coating system concept which is easier to maintain and clean.